US3912379A - Three element objective lens having asphoric surfaces on the middle element - Google Patents

Three element objective lens having asphoric surfaces on the middle element Download PDF

Info

Publication number
US3912379A
US3912379A US521226A US52122674A US3912379A US 3912379 A US3912379 A US 3912379A US 521226 A US521226 A US 521226A US 52122674 A US52122674 A US 52122674A US 3912379 A US3912379 A US 3912379A
Authority
US
United States
Prior art keywords
lens
focal length
objective lens
curvature
middle negative
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US521226A
Inventor
Donald Dejager
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eastman Kodak Co
Original Assignee
Eastman Kodak Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eastman Kodak Co filed Critical Eastman Kodak Co
Priority to US521226A priority Critical patent/US3912379A/en
Application granted granted Critical
Publication of US3912379A publication Critical patent/US3912379A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/12—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having three components only
    • G02B9/14—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having three components only arranged + - +
    • G02B9/16—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having three components only arranged + - + all the components being simple

Definitions

  • Morrow ABSIRACT A three element objective lens having a from positive biconvex element, a middle negative biconcave element and a rear positive biconvex element.
  • the first and second elements are formed of inexpensive plastic materials. Improved optical quality at a relative aperture of f/4.00 is achieved by the incorporation of an asphere on both surfaces of the middle negative element.
  • lens will be used to describe the complete lens and not the elements thereof.
  • the elements are numbered from left to right with Arabic numerals.
  • the elements, indices of refraction, N, Abb numbers V, radii of curvature R, thicknesses T, and air spaces S are numbered to correspond with the drawing.
  • the indices of refraction are for the 0.5893 micron sodium D line of the spectrum.
  • the Abb numbers are calculated utilizing the D line index and, as the main dispersion, the index difference between the 0.4861 micron hydrogen F line and the 0.6563 micron hydrogen C line. Radii of curvature having centers of curvature to the right of the surface are considered positive; those with centers of curvature to the left of the surface are considered negative.
  • the lens comprises three air spaced elements.
  • Element 1 is a front positive biconvex element.
  • Element 2 is a middle negative biconcave element.
  • Element 3 is a rear positive biconvex element.
  • D is a diaphragm.
  • An aspheric surface may be described by the following equation:
  • Lenses may be made according to this invention by following the specifications in the preferred embodiments presented below; 0
  • Example 11 illustrates a lens having a focal length of 25.76mm, with a relative aperture off/4.00 and a semifield angle of 22.52. It is similar to Example 1 in the choice of materials, the relative optical powers, and in the incorporation of an ellipsoid and a hyperboloid surface on Element 2.
  • the aspheres are characterized by the following coefficients:
  • a three element lens comprising, from front to rear, a front biconvex positive element. a middle negative element and a rear positive biconvex element, wherein said middle negative element includes two aspheric surfaces and the lens has a focal length of F, within the range of 25mm F 26mm, when the radii of curvature R, thicknesses T, air spaces S, vertex curvatures C and conic constants K, as numbered by subscript from front to rear, are as defined by the following relationships:
  • Cy 1+ 1-(1+K)C Surface C K wherein x is the sag of an aspheric surface from a plane reference surface at a radial distance y from the axis of the lens, C is equal to the reciprocal of the vertex radius of curvature R and K is the conic constant.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)

Abstract

A three element objective lens having a front positive biconvex element, a middle negative biconcave element and a rear positive biconvex element. The first and second elements are formed of inexpensive plastic materials. Improved optical quality at a relative aperture of f/4.00 is achieved by the incorporation of an asphere on both surfaces of the middle negative element.

Description

OR 3 9 912 9 379 1 I g United Stan W 9g 6/ [111 3,912,379 DeJager M 1 a 1 51 Oct. 14, 1975 [54] THREE ELEMENT OBJECTIVE LENS 3,438,697 4/1969 Melech 350/226 HAVING ASPHQRIC SURFACES ON THE 3,449,041 6/1962 Deiager 350/226 3,762.80] 10/197 Ba r 350 189 MIDDLE ELEMENT 3,868.173 2 1975 M11; et a]. 350 19 x Primary Examiner.1ohn K. Corbin Attorney, Agent, or Firm-J. Morrow ABSIRACT A three element objective lens having a from positive biconvex element, a middle negative biconcave element and a rear positive biconvex element. The first and second elements are formed of inexpensive plastic materials. Improved optical quality at a relative aperture of f/4.00 is achieved by the incorporation of an asphere on both surfaces of the middle negative element.
3 Clains, 1 Drawing Figure U.S. Patent Oct. 14, 1975 3,912,379
THREE ELEMENT OBJECTIVE LENS HAVING ASPHORIC SURFACES ON THE MIDDLE ELEMENT BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to photographic objectives and in particular to such an objective that comprises three air spaced elements.
2. Description of the Prior Art Triplets for use as photographic objectives are well known. Initially, such triplets were all glass, but later plastic materials were developed for use as lens elements, such as in US. Pat. Nos. 3,194,1l6; 3,438,697 and 3,449,041. Plastic materials have, in general, reduced the cost of photographic objectives but have accentuated certain design problems. For instance, variations in the back focal length due to thermally induced contraction and expansion of the optics may be increased.
SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawing which is a diagrammatic axial cross section of a lens according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS For all purposes of describing or claiming of the invention, the term lens will be used to describe the complete lens and not the elements thereof. In the drawing, the elements are numbered from left to right with Arabic numerals. In each of the examples, the elements, indices of refraction, N, Abb numbers V, radii of curvature R, thicknesses T, and air spaces S are numbered to correspond with the drawing. The indices of refraction are for the 0.5893 micron sodium D line of the spectrum. The Abb numbers are calculated utilizing the D line index and, as the main dispersion, the index difference between the 0.4861 micron hydrogen F line and the 0.6563 micron hydrogen C line. Radii of curvature having centers of curvature to the right of the surface are considered positive; those with centers of curvature to the left of the surface are considered negative.
In all embodiments of the invention as illustrated in the drawing, the lens comprises three air spaced elements. Element 1 is a front positive biconvex element. Element 2 is a middle negative biconcave element. Element 3 is a rear positive biconvex element. D is a diaphragm.
The use ofaspheric surfaces in a lens design provides additional parameters for correction of aberrations. lncorporation ofan aspheric surface is particularly useful in a higher relative aperture lens, because it permits a better correction of spherical aberration than is otherwise obtainable. In the design of the present invention, the improved spherical aberration correction, along with the high relative aperture, are achieved by the use of aspheres on both surfaces of the middle negative element.
An aspheric surface may be described by the following equation:
L l m This equation describes a surface in terms of its surface sag x at a semi-aperture distance y from the axis of the lens. The constant C is the vertex curvature, that is, the surface curvature at the vertex of the lens, equal to the reciprocal of the vertex radius of curvature R. The constant K is the conic constant. Certain values of K describe conic sections or surfaces of revolution about the optical axis of the lens. Higher order terms in the equation for x may also be included, if desired.
Lenses may be made according to this invention by following the specifications in the preferred embodiments presented below; 0
EXAMPLE I Radius Thickness/ Element N V mm Separation s,=i.s00 R,=9.4442 I l.49l68 57.4 T,=2.l00
s,=3.i l0 R,=Asphere 2 1.59028 30.9 T,=l .000
R.=Asphere S,=l.8l0 R,=29.49l 3 l.73400 51.0 T,=3 .200
Example I illustrates a lens having a focal length of 2500mm, with a relative aperture off/4.0, and a semifield angle of 23.l 1. Elements I and 2 are made of polymethyl methacrylate and polystyrene respectively, while Element 3 is made of a higher index glass material. The choice of materials and the relative optical powers of Elements 1 and 2 are designed to compensate for the index change caused by thermal shifts, so that the back focal lengthof the lens is relatively insensitive to changes in temperature. This permits design of a lens having a higher relative aperture, even though the thermal effects on such lenses are accentuated by the decrease in depth of focus. The aspheres on the surfaces of Element 2 are an ellipsoid and a hyperboloid characterized by the following coefficients:
Example 11 illustrates a lens having a focal length of 25.76mm, with a relative aperture off/4.00 and a semifield angle of 22.52. It is similar to Example 1 in the choice of materials, the relative optical powers, and in the incorporation of an ellipsoid and a hyperboloid surface on Element 2. The aspheres are characterized by the following coefficients:
Table [1 Surface C K While there are many ways to judge the optical performance of a particular lens, one criteria is the image formed of a point object, with the size of the image taken as the diameter of the circle which contains 50 percent of the rays. Light rays of three different wavelengths, 0.44, 0.55 and 0.65 micron, were utilized in the relative ratio :50:35. Rays were traced at six different field angles through each lens. The parameters illustrated in Table [[1 illustrate the results of these computations for the lenses of Examples 1 and 11 in comparison with lenses which are presently available. Sample 1 is an EKTAR four element lens made of glass with an effective focal length of 26mm and a relative aperture off/2.7. Sample 2 is an EKTAR three element lens, made of plastic and glass, with an effective focal length of 26mm and a relative aperture off/5.6.
By comparison of the spot diameters illustrated in Table 111, it may be seen that the plastic-glass triplets utilizing aspheric surfaces on Element 2 are close in optical quality to lens samples 1 and 2. Note the improved optical performance near the axis, due to improved correction of spherical aberration. Also note that at 75% field, the optical quality of Examples 1 and 2 are slightly inferior to Samples 1 and 2. This is a result of astigmatism, related to the fact that the astigmatic node was shifted to the 90% field position, whereas in Sample lenses 1 and 2 the astigmatic node occurred at about field. Consequently, Examples 1 and 2 are again close to lens Samples 1 and 2 in optical quality of field.
The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
1 claim:
1. A three element lens comprising, from front to rear, a front biconvex positive element. a middle negative element and a rear positive biconvex element, wherein said middle negative element includes two aspheric surfaces and the lens has a focal length of F, within the range of 25mm F 26mm, when the radii of curvature R, thicknesses T, air spaces S, vertex curvatures C and conic constants K, as numbered by subscript from front to rear, are as defined by the following relationships:
2. A lens as in claim 1, wherein said lens has a focal length of 25.00mm when constructed according to the following parameters:
Radius Thickness/ Element N V mm Separation S =l .500 R,=9.4442 1 1.49168 57.4 T,=2.100
S =3.1 10 R =Asphere 2 1.59028 30.9 T,=l.000
R.=Asphere S,=1.810 R,=29.491 3 1.73400 51.0 T;=3.200
-Continued Surface C K c 0.0900386 2 3l76ll 4 0.1139004 1 .869075 wherein x is the sag of an aspheric surface from a plane reference surface at a radial distance y from the axis of the lens, C is equal to the reciprocal of the vertex radius of curvature R and K is the conic constant.
3. A lens as in claim 1, wherein said lens has a focal length of 25.76mm when constructed according to the following parameters:
Radius Thickness or Element N,, V mm Separation mm S,=l.500 R =l0.053 l l.49l68 57.4 T,=2.l
S,=3.290 R =Asphere 2 l.59028 30.9 T,=l .000
R.=Asphere S;=l .790 R,=3 l .668 3 1,73400 5l.0 T -3.260
Cy 1+ 1-(1+K)C= Surface C K wherein x is the sag of an aspheric surface from a plane reference surface at a radial distance y from the axis of the lens, C is equal to the reciprocal of the vertex radius of curvature R and K is the conic constant.

Claims (3)

1. A three element lens comprising, from front to rear, a front biconvex positive element, a middle negative element and a rear positive biconvex element, wherein said middle negative element includes two aspheric surfaces and the lens has a focal length of F, within the range of 25mm < OR = F < OR = 26mm, when the radii of curvature R, thicknesses T, air spaces S, vertex curvatures C and conic constants K, as numbered by subscript from front to rear, are as defined by the following relationships:
2. A lens as in claim 1, wherein said lens has a focal length of 25.00mm when constructed according to the following parameters:
3. A lens as in claim 1, wherein said lens has a focal length of 25.76mm when constructed according to the following parameters:
US521226A 1974-11-05 1974-11-05 Three element objective lens having asphoric surfaces on the middle element Expired - Lifetime US3912379A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US521226A US3912379A (en) 1974-11-05 1974-11-05 Three element objective lens having asphoric surfaces on the middle element

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US521226A US3912379A (en) 1974-11-05 1974-11-05 Three element objective lens having asphoric surfaces on the middle element

Publications (1)

Publication Number Publication Date
US3912379A true US3912379A (en) 1975-10-14

Family

ID=24075906

Family Applications (1)

Application Number Title Priority Date Filing Date
US521226A Expired - Lifetime US3912379A (en) 1974-11-05 1974-11-05 Three element objective lens having asphoric surfaces on the middle element

Country Status (1)

Country Link
US (1) US3912379A (en)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3127140A1 (en) * 1980-07-11 1982-03-04 Canon K.K., Tokyo Zoom (varifocal) lens
US4384766A (en) * 1980-06-17 1983-05-24 Canon Kabushiki Kaisha Optical system for copying
US4522471A (en) * 1982-08-20 1985-06-11 Olympus Optical Co., Ltd. Adapter lens system for use with photographic cameras
US4542961A (en) * 1983-03-03 1985-09-24 Canon Kabushiki Kaisha Triplet type objective
US4557567A (en) * 1982-01-11 1985-12-10 Hitachi, Ltd. Lens system with plastic lenses compensating for temperature changes
US4620775A (en) * 1984-09-26 1986-11-04 Ricoh Company, Ltd. Front-diaphragm wide angle lens
US4659187A (en) * 1982-10-29 1987-04-21 Canon Kabushiki Kaisha Zoom lens using elements made of plastic materials
US4671626A (en) * 1984-03-21 1987-06-09 Minolta Camera Kabushiki Kaisha Photographic lens system
GB2188167A (en) * 1986-03-19 1987-09-23 Combined Optical Ind Ltd Biaspherical lens
US4733953A (en) * 1985-02-06 1988-03-29 Matsushita Electric Industrial Co., Ltd. Color corrected projection lens
US4758074A (en) * 1985-04-27 1988-07-19 Minolta Camera Kabushiki Kaisha Video projector lens system
US4787724A (en) * 1986-02-07 1988-11-29 Minolta Camera Kabushiki Kaisha Triplet type objective with a diaphragm arranged behind the lens system
US5596455A (en) * 1995-06-29 1997-01-21 Minnesota Mining And Manufacturing Company Fixed-focus triplet projection lens for overhead projectors
US5835288A (en) * 1996-05-13 1998-11-10 Fuji Photo Optical Co., Ltd. Imaging lens
US6441971B2 (en) * 1999-09-27 2002-08-27 Alex Ning Compact lens with external aperture stop
US20030193605A1 (en) * 2002-03-25 2003-10-16 Konica Corporation Image-capturing lens, image-capturing device and image capturing unit
US6788473B2 (en) * 2000-12-07 2004-09-07 Samsung Electronics Co., Ltd. Objective lens device for correcting chromatic aberration and optical pickup employing the same
US7672045B2 (en) 2007-08-23 2010-03-02 Goodrich Corporation Compact two-element infrared objective lens and IR or thermal sight for weapon having viewing optics
WO2014014338A1 (en) * 2012-07-16 2014-01-23 Mimos Berhad Compound lens for solar heat collection
CN109031591A (en) * 2018-07-24 2018-12-18 瑞声光电科技（苏州）有限公司 Projection lens
US11204482B1 (en) * 2020-08-28 2021-12-21 Yejia Optical Technology (Guangdong) Corporation Large-aperture optical lens with three lens pieces

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194116A (en) * 1961-12-22 1965-07-13 Eastman Kodak Co Triplet objective having a negative element formed of a copolymer of acrylonitrile and styrene
US3438697A (en) * 1967-01-23 1969-04-15 Eastman Kodak Co Wide-angle triplet objective
US3449041A (en) * 1967-01-23 1969-06-10 Eastman Kodak Co Triplet-type objective lens
US3762801A (en) * 1972-02-24 1973-10-02 Polaroid Corp Compact three component objective lenses
US3868173A (en) * 1973-01-18 1975-02-25 Ambatis Maris Objective lens assembly for projection television

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194116A (en) * 1961-12-22 1965-07-13 Eastman Kodak Co Triplet objective having a negative element formed of a copolymer of acrylonitrile and styrene
US3438697A (en) * 1967-01-23 1969-04-15 Eastman Kodak Co Wide-angle triplet objective
US3449041A (en) * 1967-01-23 1969-06-10 Eastman Kodak Co Triplet-type objective lens
US3762801A (en) * 1972-02-24 1973-10-02 Polaroid Corp Compact three component objective lenses
US3868173A (en) * 1973-01-18 1975-02-25 Ambatis Maris Objective lens assembly for projection television

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4384766A (en) * 1980-06-17 1983-05-24 Canon Kabushiki Kaisha Optical system for copying
DE3127140A1 (en) * 1980-07-11 1982-03-04 Canon K.K., Tokyo Zoom (varifocal) lens
US4557567A (en) * 1982-01-11 1985-12-10 Hitachi, Ltd. Lens system with plastic lenses compensating for temperature changes
US4522471A (en) * 1982-08-20 1985-06-11 Olympus Optical Co., Ltd. Adapter lens system for use with photographic cameras
US4659187A (en) * 1982-10-29 1987-04-21 Canon Kabushiki Kaisha Zoom lens using elements made of plastic materials
US4542961A (en) * 1983-03-03 1985-09-24 Canon Kabushiki Kaisha Triplet type objective
US4671626A (en) * 1984-03-21 1987-06-09 Minolta Camera Kabushiki Kaisha Photographic lens system
US4620775A (en) * 1984-09-26 1986-11-04 Ricoh Company, Ltd. Front-diaphragm wide angle lens
US4733953A (en) * 1985-02-06 1988-03-29 Matsushita Electric Industrial Co., Ltd. Color corrected projection lens
US4758074A (en) * 1985-04-27 1988-07-19 Minolta Camera Kabushiki Kaisha Video projector lens system
US4787724A (en) * 1986-02-07 1988-11-29 Minolta Camera Kabushiki Kaisha Triplet type objective with a diaphragm arranged behind the lens system
GB2188167A (en) * 1986-03-19 1987-09-23 Combined Optical Ind Ltd Biaspherical lens
US5596455A (en) * 1995-06-29 1997-01-21 Minnesota Mining And Manufacturing Company Fixed-focus triplet projection lens for overhead projectors
US5835288A (en) * 1996-05-13 1998-11-10 Fuji Photo Optical Co., Ltd. Imaging lens
US6441971B2 (en) * 1999-09-27 2002-08-27 Alex Ning Compact lens with external aperture stop
US6788473B2 (en) * 2000-12-07 2004-09-07 Samsung Electronics Co., Ltd. Objective lens device for correcting chromatic aberration and optical pickup employing the same
US20030193605A1 (en) * 2002-03-25 2003-10-16 Konica Corporation Image-capturing lens, image-capturing device and image capturing unit
US7196855B2 (en) * 2002-03-25 2007-03-27 Konica Corporation Image-capturing lens, image-capturing device and image capturing unit
US7672045B2 (en) 2007-08-23 2010-03-02 Goodrich Corporation Compact two-element infrared objective lens and IR or thermal sight for weapon having viewing optics
US20100165455A1 (en) * 2007-08-23 2010-07-01 Goodrich Corporation Compact two-element infrared objective lens and IR or thermal sight for weapon having viewing optics
US7848015B2 (en) 2007-08-23 2010-12-07 Goodrich Corporation Compact two-element infrared objective lens and IR or thermal sight for weapon having viewing optics
WO2014014338A1 (en) * 2012-07-16 2014-01-23 Mimos Berhad Compound lens for solar heat collection
CN109031591A (en) * 2018-07-24 2018-12-18 瑞声光电科技（苏州）有限公司 Projection lens
US11204482B1 (en) * 2020-08-28 2021-12-21 Yejia Optical Technology (Guangdong) Corporation Large-aperture optical lens with three lens pieces

Similar Documents

Publication Publication Date Title
US3912379A (en) Three element objective lens having asphoric surfaces on the middle element
US3944337A (en) Three element objective lens with ellipsoidal, hyperbolic, and parabolic surfaces
US4189211A (en) Wide angle telecentric projection lens assembly
US2520635A (en) Optical system
JPS6049313A (en) Reflection refraction lens
US3972592A (en) Zoom projection lens
US3967884A (en) Three element objective lens
JPH07294808A (en) Image forming lens
US2440088A (en) Optical lens system
US4892398A (en) Triplet type objective with a diaphragm arranged behind the lens system
US2735339A (en) Yoshikazu doi
US3910685A (en) Three element objective lens with aspheres on rear surfaces of first and second elements
US3486805A (en) Ultra-achromatic fluorite silica triplet lens system
US5502597A (en) Wide-angle photographic lens system and a photographic camera
US3722979A (en) Optical system of the real image type for finders having aspheric surfaces
US2416032A (en) Optical objective
US2576011A (en) Catadioptric optical system
US3905686A (en) Three element projection lens
US2865252A (en) Wide field objective comprising four highly meniscus elements
US2983193A (en) High resolution photographic objectives
US3975087A (en) Four element microscope objective
US2421927A (en) Optical objective of the telephoto type
US2500046A (en) Petzval-type photographic objective
JPH0536765B2 (en)
JPS6142245B2 (en)